Reminder: Don’t Buy Premium If You Don’t Need It

Some car myths never really seem to go away, and one of the most pervasive is that you should fill your regular-gasoline-rated car with premium gas, because it increases your fuel economy or horsepower. However, according to new research by AAA, using more expensive premium gas on vehicles that don’t require it is just throwing money away.

Interestingly, according to AAA’s research, this myth is so hard to extinguish because it holds a grain of truth in it—AAA found that fuel economy did increase in the vehicles tested, but by a tiny amount: an average of just 2.7%; and horsepower did rise, but by a similarly piddly amount: an average of just 1.4%.

AAA then pointed out that any savings from the increased fuel economy were more than offset by the much higher price for premium gas—according to AAA, the premium-grade gas often sells for 20-25% more than regular.

Also, AAA added that this does not apply to vehicles that require premium. In those engines, using the higher-octane fuel allows them to run at a higher compression ratio without causing engine knock, leading to more energy in the cylinder. Using regular gas in one of those engines could cause significant fuel economy and power decreases, and eventually engine and emissions control system damage.